The invention relates to image marking machines and more particularly to the use of paper travel diagnostics in image marking machines.
It is important to the maintenance of complex electronic equipment such as reproduction machines to reduce the service calls and time spent in monitoring and maintaining the machine operation, in particular reducing the cost of maintenance and service.
Diagnostic procedures related to sheet travel are already well known. For example, it is known to use sensors to detect the presence of paper sheets traveling along the paper path, a memory for storing electrical representations of time for the sheet to travel between the sensors, and a display for indicating the sheet travel time.
It is also known that time periods of paper path travel between various sensors can be displayed for a previous copy run. U.S. Pat. No. 4,335,949 discloses a reproduction machine having a recirculating document handler, a display, and the means to enter a diagnostic mode for immediate access to time periods between sensors detecting document travel in the document handler. Upon entering the diagnostic mode, the first requested event of six events or time periods is displayed, the display providing the number of the event and the time period in milliseconds.
In addition, U.S. Pat. No. 4,589,705 discloses a method for adjusting the operational timing of the copy sheet feeder in a reproduction machine by determining the current copy sheet feeding time interval required for the copy sheet feeder to advance a copy sheet to a predetermined point in the copy processing path following actuation thereof by the machine control system. The control then compares the current copy sheet feeding time interval with an optimum copy sheet feeding time interval stored in the machine memory, and adjusts the sheet feeder timing so that the sheet feeding time interval of the sheet feeder substantially equals the optimum copy sheet feeding time interval stored in the machine memory.
U.S. Pat. No. 4,627,711 discloses a control data base including a packet phase describing the origin and destination and all specific details of how each individual copy sheet is to move through the system, a tracker phase showing the current physical location of the sheet in the system, wherein both the lead edge and the trail edge of each sheet is tracked and dynamically updated at each control point, and a fault phase showing that a fault has been responded to by the system.
Xerox Disclosure Journal, Vol. 9, No. 6 Nov/Dec 1984 discloses that the actual transport time (between sensors) from the initial acquisition of a document to its positioning on the platen can be measured for a recirculating document handler. This information is then used to provide a specific maximum or total time to be allowed by the control system of that copier for each document exchange (called the feed-to-flash time). This was in lieu of the standard practice of presetting a much longer fixed allowed time for all document exchanges, which fixed time was calculated for the worst conditions.
A difficulty with the prior art systems is that once a control time period or window is set, for example, between sensors in a specific machine, this time period or window cannot be varied in that particular machine. For diagnostic purposes, however, it would often be desirable to be able to expand a control time period or window. Often time, a fixed control window for viewing the time period between sensors does not provide enough flexibility for a service representative to diagnose a situation. For example, if the time elapsed for a document or copy sheet to traverse between a pair of sensors exceeds the normal or accepted control window, an error signal will be generated and stored in memory for later display to the Service Representative. However, it is often important for the Service Representative to be able to diagnose the degree of deviation from the normal, to know if the elapsed time was substantially greater or only slightly greater than the normal window. This could often indicate to the Service Representative the source of the malfunction, such as an electrical or mechanical source. In prior art control systems, the Service Representative is not able to determine the degree of deviation and better able to pinpoint the source of malfunction.
It is an object of the present invention, therefore, to provide a new and improved control and diagnostic method that expands the normal fixed windows or time periods in the operation of a machine when the machine is in a diagnostic mode.
Further advantages of the present invention will become apparent as the following description proceeds, and the features characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.
Briefly, the present invention is a technique for expanding the control windows or time periods between sensors in a real time machine for diagnostics. In particular, upon indication of a malfunction of the travel of a sheet between sensors, a Service Representative is able to place the machine in a diagnostic mode and expand the time period or window for determining more precisely the degree of deviation of the errant time period from the standard range.